Pulp molding



March 7, 1939. H. v. MITCHELL PULP MOLDING Filed Aug. 27, 1936 3Sheets-Sheet 1 Z M m T M k m V a 1 Wm fl ATTORNEY March 7, 1939. vMITCHELL 2,149,878

PULP MOLDING Filed Aug. 2'7, 1936 5 Sheets-Sheet 2 mmlgle mmmlim mmm 4'0IVEOR Harvey Ffizlcitz/l ATTO R N EY March 7, 1939. H. v. MITCHELL PULPMOLDING Filed Aug. 27, 1936 3 Sheets-Sheet 5 ATTORNEY interior surface.

Patented Mar. 7, 1939 UNITED STATES PATENT OFFICE Application August 27,

15 Claims.

This invention relates generally to pulp molding and more particularlyto a process and apparatus for producing pulp articles molded toultimate shape without the prior formation of flat sheet stock.

In accordance with the invention, articles may be molded with extremelyhigh speed, which is a requisite to meet the demands of cheapness incommercial production. The articles capable of being produced may behollow and have irregular shapes. Furthermore, the invention lendsitself admirably to the production of hollow containers of relativelythin walls, both with and without restricted openings. Or, if desired,articles having thick walls may be produced.

Among the various features of the invention is the production ofcontainers having a smooth This is accomplished without undue loss inspeed by a method hereinafter to be described in more detail, wherebythe stock from which the articles are produced is introduced into aforaminous mold in a stream under a controlled velocity head. Theforaminous mold 'is surrounded by a jacket in which is maintained acontrolled sub-atmospheric pressure. At the beginning of the moldingprocess, by reason of the sub-atmospheric pressure in the jacketsurrounding the foraminous mold, the tendency of the liquid carrying thepulp fibres is to fiow outwardly through the holes of the mold walls.Consequently, the pulp fibres are retained on the walls of the moldwhile the liquid passes through its pores. As the molding processcontinues the thickness of the fibrous blanket increases whilesimultaneously the resistance to the flow of liquid through the fibrouswall into the jacket increases. Provision is made for flowing pulp stockout of the mold while the fresh stock from the supply tank is beingintroduced. Hence, the particles of pulp are energized with a velocityhead which tends to maintain them in motion. As the fibrous wall beingbuilt up on the walls of the mold increases in thickness with resultantincrease in resistance to the fiow of liquid through the foraminouswalls of the mold, there finally reaches a condition when the velocityhead of the particles or pulp fibres is greater than the force tendingto draw the pulp fibres to the wall of the mold. When this conditionexists the excess stock, including fibres, pass out of the mold, leavinga wall of pulp fibres on the interior surface of the mold, the thicknessof which may be predetermined by adjustments to be describedhereinafter.

Therefore, in accordance with the invention, there is a selectivedeposition of pulp fibres upon the walls of the mold which permits ofthe production of hollow articles having smooth interior surfaces sincethe lumps or clots of fibres, almost invariably present in pulp stockmade up for 1936, Serial No. 98,181

commercial use, are washed away from the walls and, if desired, maybereturned to the pulp supply tank together with the excess stockmentioned in the foregoing. At the same time, there is a washing of thefibrous blanket tending to smooth out the fibres and mat them, resultingin a further smoothing'out of the interior surface of the article beingformed.

It will be understood that the procedure just described will requireonly a few seconds, after which the stream of pulp stock may be cut offor the mold removed from a continuous stream of pulp stock, when thearticle so formed may be given a treatment to remove carrier liquid fromthe built-up wall. Finally, the article may be given further treatmentas desired, whereby to impart thereto certain advantageouscharacteristics, depending upon the use for which the article isintended.

Although the novel features which are believed to be characteristic ofthis invention will be particularly pointed out in the claims appendedhereto, the invention itself, as to its objects and advantages, and themanner in which it may be carried out, may be better understood byreferring to the following description taken in connection with theaccompanying drawings forming a part thereof, in which:

Fig. 1 is a plan view of one form of appaartus;

Fig. 2 is a view in elevation partly in section of the apparatus shownin plan in Fig. 1;

Fig. 3 is a view in cross-section of a three-way Fig. 9 is a view inperspective of a part of the separable mold; and

Fig. 10 is a view in cross-section of the separable moldf In thefollowing description and in the claims, various details will beidentified by specific names for convenience, but they are intended tobe as generic in their application as the art will permit. Likereference characters denote like parts in the several figures of thedrawings.

Referring now to the drawings, l0 represents a pulp supply tank in whichis maintained a supply of pulp stock I l of desirable concentration.Leading from the supply tank I0 is a conduit I2 connected with thesuction side of a centrifugal pump l3. Connected to the discharge sideof the centrifugal pump I3 is a discharge conduit [4 passing upwardlythrough the tank and terminating in a threaded opening l5. A jet isthreaded at its lower end I! is screwed into the threaded opening l5 ofthe discharge conduit, which provides for vertical movement andadjustment of the jet I6. The opposite upper end 18 of the jet I6 isthreaded. A disc 19, which may be circular and have a fiat surface 20,is provided with a threaded opening 2! and screwed on the threads N.This provides for vertical movement and adjustments of the plate surface2|].

Intermediate the centrifugal pump 03 and the jet l6 and positionedwithin the tank I0 above the surface of the pulp stock ii there is ,aby-pass conduit 22 connected with the discharge conduit it ofthe.centrifugal pump 13. This by-pass conduit is equipped with a by-passvalve 23.

Fixed to the tank is a. bracket 24 upon which is mounted a moldingdevice represented generally by reference character M carrying anactuating mechanism. The mold 25 itself is fixed within a jacket 21. Thejacket 21 is provided with a threaded opening 28 screwed onto a conduit29, which in turn is fixed to a hub 30. The hub 30 is fixed to acylindrical axle 3|, which in turn is mounted in a. bearing 32. Fixed tothe axle 35 is a crank 33 provided with a pin 34, which in turn ismovably connected to an actuating arm 35. The opposite end of the arm 35is connected to the end of a solenoid arm 35' which projects into asolenoid. A spring 31 mounted on the arm 35' between the solenoid andshoulder 9 tends to maintain the actuating arm 35 in the position shownin Fig. 1, When current is passed through the solenoid 36 fromconnecting wires 38 and 39, the actuating arm35 is drawn toward thedirection of the solenoid 36 and consequently actuates the crank 33,which in turn causes the mold 25 to revolve horizontally about the pivotprovided by the axle 3!. Also connected to the actuating arm 35 is avalve actuating arm 40 connected at one end by a pin 41. The oppositeend of the valve actuating arm- 46 is provided with a slot 42 engaging apin 63 fixed to a valve stem actuating arm 44 fixed at 45 to the valvestem 46. A spring 8 tends to hold the valve stem actuating arm 44 in theposition shown in Fig. 1.

The valve 41 has a valve plug 38 provided with a passageway 49. Thevalve housing is provided with three openings 5|, 52 and 53. Screwed inthe opening 5| is a nipple 54 to which is connected a conduit 55 whichmay, if desired, be flexible. The opposite end of the conduit 55 isconnected likewise with an opening 56 in the conduit 29.

The opening 52 in the valve housing is likewise provided with a nipple51 to which is connected a conduit 58 leading to a supply of air undersuper-atmospheric pressure (not shown). The remaining opening 53 in thevalve housing is likewise provided with a nipple 59, which is connectedwith a conduit 60, which also, if desired, may be flexible. The conduit60 on its opposite end is connected with a nipple 6! leading into avacuum tank 62, provided with a gauge '63 and a suction line 64 leadingto a vacuum pump 65. The vacuum tank is provided with a water drawofi66.

The vacuum pump is operated by prime mover 66, which may be an electricmotor. The vacuum pump is operated by pulley 61 on the vacuum pump andpulley 68 on the motor connected by a belt 69. The motor 66 is connectedby pulley l6 and pulley H on the centrifugal pump and a belt I2, whichserves to operate the centrifugal pump i3.

The solenoid 36 hereinbefore mentioned may be connected with a timeclock arrangement indicated by 13 whereby the molding device representedgenerally by the reference character H and valve 41 may be actuated intimed relation.

The molding apparatus just described may be operated as follows: Asuitable supply of pulp stock is charged into the tank H. The term "pulpstock in this connection has reference to a suspension of pulp fibres inwater or other suitable carrying liquid as it is discharged from theheaters. Various types of pulp stock may be used and the concentrationand other characteristics will be determined by the type of article tobe formed and the characteristics which it is desired to impart thereto.

After the supply tank is charged with a suitable supply of pulp stockthe motor 66 is placed in operation, which in turn operates the vacuumpump 65 and the centrifugal pump [3. Consequently the pulp stock isdischarged upwardly through the conduit l4. If desired, the entiredischarge of the centrifugal pump may be directed through the jet l6 bycompletely closing the by-pass valve 23. On the other hand, byregulating the opening in the by-pass valve 23 the flow of pulp throughthe jet may be regulated as desired. It will be apparent that the pulpstock being discharged from the jet l6 will take the form of a geyser orfountainlike column which spreads umbrellawise and flows laterally anddownwardly in a stream over the interior surface of the mold. The heightof the geyser may be regulated by adjustment of the by-pass valveopening.

Having adjusted the geyser at a desirable height the plate 20 may bealso adjusted as to height, to adjust within limits, the rate of flow ofpulp stock out of the mold. The time clock arrangement may then be setin operation. It will be understood that it is suitably connected withthe solenoid 36. When the current is oil? the solenoid 36, the mold willtake a position directly over the geyser of pulp stock. Meantime thevalve plug 48 takes the position as shown in Fig. 3, in which the jacketchamber 15 is openly connected through conduit 29, 55, passageway 49,conduit 60, into the vacuum tank 62. Under these conditions, thetendency of the pulp stock is to fiow through the pores of the walls ofthe foraminous mold 25. The walls of the mold, however, retain the pulpfibres immediately adjacent thereto and the liquid fiows into the vacuumchamber 15 of the jacket 21, through the conduits just mentioned intovacuum tank 62. As the pulp is deposited upon the walls of theforaminous mold, there is a gradual increase of resistance against flowof the pulp stock toward the walls of the mold. Finally, the pulpfibrous blanket, which is thus built up upon the interior surface of thewalls of the foraminous mold offers sufficient resistance to a furtherde-' posit of pulp fibres that the velocity head on the particlesprovided by the jet I6 is greater than the force tending to draw thefibres toward the interior surface of the walls of the foraminous mold.When this condition is reached, the excess pulp stock is flowing out ofthe mold through the space 16 between the bottom wall ll of the jacket21 and the upper surface 20 of the plate l9. It will be observed thatthe velocity head of the stream of pulp flowing in and out of the moldmay be regulated within limits by adjusting the by-pass valve 23 and thespace 16 between the bottom I1 of the jacket 21 and the upper surface 20of the plate I9. It'will be understood that, when the proper conditionsof operation are determined, these adjustments are maintained and it isnot necessary to change the adjustment during the molding operation informing'a. hollow pulp article. It will be understood also that theamount of vacuum may be controlled. Ordinarily, the greater the vacuum,the thicker will be the thickness of pulp wall built up, otherconditions remaining constant. 1

As the desired quantity of pulp fibres has been deposited upon the innersurface of the walls of the foraminous mold 25, there is meantime aselective deposition of pulp fibres upon the fibrous blanket beingformed and clots and lumps of pulp fibres which may be present in thepulp stock are Washed away and returned to tank I I. Consequently, thereis a resultant smoothing out of the interior surface of the pulp wallwhich has been thus built up.

Next, electric current is permitted to flow through the solenoid 36,through the connecting wires 38 and 39 from a suitable source of power(not shown). The interval of flowing current may be controlled by thetime clock arrangement. This causes actuation of the arm 35 toward thesolenoid, which in turn operates the crank 33 and revolves the moldingdevice 14 in a horizontal plane about the axis of the axle 3I.Consequently, the mold itself is moved away from the geyser 18.Meantime, the conduits 29, 55, passageway 49, and conduit 60 remain openfor a short period, which is determined by the length of the slot 42 inthe arm 40. During this time, water in the pulp blanket which has beenformed is further extracted and the liquid is drawn into the vacuum tank62. Finally, the arm 40 actuates valve stem arm 44, which in turnrevolves the valve stem 46 and valve plug 48, in such manner thatpassageway 49 takes the position shown in dot-dash lines at 50, thusconnecting with conduits 58 and 55. Since conduit 50 is connected with asupply of air under superatmospheric pressure, pressure is built up inthe jacket chamber 15 and loosens the container which has beenpreviously formed on the walls of the mold. The container may then bedischarged from the mold and the current is cut oil from the solenoid.By reason of the spring 31, the molding device is again actuated in theopposite direction, returning the mold to its original position over thegeyser, and the cycle may be repeated. A stop pin 19 fixed to the hub 30registers with a groove 80 in the crank 33 to limit the movement of themolding device represented generally by the reference character 14.

While automatic mechanism has been disclosed whereby the molding devicemay be actuated, it will be apparent that in some instances automaticmechanism is unnecessary and the mold may be moved in and out of contactwith the pulp geyser manually and the valve operating the vacuum andpressure may also be operated by hand.

The modifiedform of apparatus illustrated in Figs. 5, 6 and 7 is similarto that disclosed in Figs. 1 and 2, except that the molding devicemechanism is designed to operate the mold vertically over the geyser,rather than in a horizontal plane as described hereinbefore.

The molding device represented generally by the reference character Icomprises a bracket 99 upon which is mounted two posts IM and I02.

The twin sleeve I03 is designed to operate vertically upon the postsIOI- and I02. This sleeve takes the form of a cross-head. The mold is'fixed in a jacket, as previously described, and

the jacket is connected to a conduit I29 and a flexible conduit I55,which in turn is connected with valve I41. This valve I41 is similar tothe valve 41 previously described. The cross-head I03 is connected witha cross-head actuating arm I04, which is provided at its upper end witha cam roller I05. A cam pulley I06 is mounted in a shaft I01, which inturn is mounted in a bearing I08, fixed to the standard I09 supportingthe valve I41. Connected to the shaft I01 is a drive pulley I I0connected by a belt II I, which in turn is connected with a prime mover(not shown). The cam roller I operates in a cam groove II2. Also mountedon a standard I09 is a valve actuating lever I I3 movably mounted on apivot pin II4 fixed to a shoulder II5, which in turn is fixed to astandard I09. The valve actuating lever is provided with a slot II6,which in turn is connected with a pin II1 fixed to a valve stemactuating arm II 8 connected at its opposite end to valve stem H9. Thevalve actuating lever I I3 is provided with a cam roller I20, whichoperates on a cam track I2I on the cam pulley I06.

With reference to the movement of the pulp stream the operation of thismolding apparatus is similar to that previously described. The mold,however, moves vertically in and out of contact with the pulp stockgeyser. The pulley H0 is placed in operation, which in turn revolves thecam pulley I06 about the axis of the shaft I01. When the cams are in theposition as shown in Fig. '7 the mold is in its lowermost position andthe depositing of pulp on the walls of the mold is taking place. As thecam pulley revolves and the cam roller I05 reaches the position I2I thethe mold is raised vertically away from the pulp geyser. Cam roller I20in the meantime allows the suction to continue for a short period afterthe mold is moved away from the pulp stock geyser and when it reaches apoint I22 on the cam track I2I valve I41 is actuated. This further drawswater from the fibrous wall built up in the mold. The vacuum is cut offand there may be a slight dwell. When the point I23 of the cam track I2Ireaches the cam roller I20 the valve I4! is actuated in such manner thatthe air pressure flow through the valve I41 into the jacket chambersurrounding the mold and the article which has been formed is loosenedand discharged from the mold. As the cam pulley continues in itsmovement the empty mold is returned to the geyser and the cycle may berepeated.

It will be understood that hollow articles with restricted openings maybe made by suitable design of the foraminous mold. Such a mold may takethe form shown in Figs. 8, 9 and- 10. The mold may comprise separableparts, mounted in a cylindrical jacket 221. .Supporting the side wallsof the mold are a series of ribs 203. As shown there are two lateralelements 200 and 20I forming halves of the side wall of the mold.Cooperating with these members is a foraminous bottom piece 202 and toppiece 203. The top piece 203 is fixed to the jacket bottom 204 and isprovided with an opening 205 into the mold cavity 206. The bottom pieceabuts projections 201 extending from the ribs 203. The ribs may bereinforced by semi-circular rings 208 and 209, so that the structurewithin the jacket comprises two principal members each including half ofthe mold itself. The bottom member 202 may, if desired, be secured toone of these members or may be a separate part. These members formingthe mold may be easily assembled and slipped into the jacket 221. Aseparable closure member 210 may be inserted over the end of the jacket22'! and made air tight by means of bolts and wing nuts 2| I. A gasket2l2 may be inserted between the jacket walls and the closure. The jacketis connected with a conduit 229 which corresponds with conduit 29previously referred to.

It will be seen from the foregoing description that the inventionprovides a process which is rapid in its operation. Articles may beformed in a cycle not requiring more than 5 to seconds and in someinstances less, yet by reason of the selective deposition of fibres fromthe pulp stream, there results a very desirable smooth interior surfaceon the containers thus produced. Furthermore, the machine and process ofthe invention are admirably suited to produce articles having walls ofvarious thicknesses.

If desired, the articles may be treated with suitable coatings orfillers to render them oil and water proof. In some instances thecoatings may be applied to the articles while still comparatively wet inthe mold, and prior to ultimate removal of the carrier liquid from thewalls of the article.

While certain novel features of the invention have been disclosed andare pointed out in the annexed claims, it will be understood thatvarious omissions, substitutions and changes may be made from the spiritof the invention.

- What is claimed is:

1. Apparatus for molding articles of fibrous material comprising aliquid stock tank for said flbrous material, a hollow foraminous moldhaving a downwardly directed mouth for receiving said fibrous material,a jacket surrounding said mold, an upwardly pointing jet beneath saidmold adapted to project the liquid stock upwardly in the form of ageyser, means for moving liquid stock from said tank in a stream ofcontrolled velocity head through said jet into the interior of saidmold, and means for controlling the amount of fibers deposited on thewalls of said mold including mechanism for maintaining a sub-atmosphericpressure in said jacket and a baille adjacent the mouth of said mold toregulate the flow of fibrous stock out of said mold under controlledvelocity head.

' 2. Apparatus for molding hollow pulp articles which comprises a supplytank for pulp stock, a hollow foraminous mold shaped to define a mold Jcavity and having a downwardly disposed restricted pulp chargingopening, a jacket about said mold, means for maintaining a vacuum withinsaid jacket, means including a pulp stock pump for moving said pulpstock from said supply tank, a vertically disposed jet on the dischargeside of said pump to project a column of pulp stock upwardly throughsaid restricted opening into the interior of said mold in the form of ageyser spreading umbrellawise, and means including a by-pass on thedischarge side of said pump for controlling the velocity head of saidpulp stock in and out of the restricted opening of said mold while pulpfibres are being deposited on the walls of said mold-from said geyser.

3. Apparatus for molding hollow .pulp articles which comprises a supplytank for pulp stock, a foraminous mold above said tank, a jacketsurrounding said mold, a vacuum tank, a conduit connecting said vacuumtank to said jacket for by those skilled in the art without departingmaintaining a sub-atmospheric pressure within said jacket, meansincluding a conduit for moving said pulp stock from said. supply tank, ajet having a vertically adjustable baflle thereon on the end of saidsecond mentioned conduit to discharge pulp stock therefrom in the formof a controlled fountain-like column flowing toward and away from saidmold, and means for moving said mold in and out of contact with pulpstock discharged from said jet.

4. Apparatus for molding hollow pulp articles comprising a supply tankfor pulp stock, a hollow foraminous mold, a jacket about said mold,means for maintaining a sub-atmospheric pressure within said jacket, aconduit leading from said supply tank, means for moving said pulp stockfrom said supply tank through said conduit, a discharge opening in saidconduit adapted to discharge pulp stock from said conduit in ageyser-like column, means for controlling the height of said column tocause it to break and spread said pulp stock laterally and downwardly ina continuous flowing stream over the interior surface of said mold,means for moving said mold in and out of contact with said geyser-likecolumn of pulp stock and means including a plate adjacent said moldandsaid discharge opening for partial adjustment of the velocity head ofpulp stock flowing out of said mold after a blanket of pulp .has beendeposited on said interior surface from said flowing stream.

5. Apparatus for molding hollow articles from pulp stock whichcomprises, a supply tank for said stock, an upwardly disposed stationaryjet communicating with said tank and through which a stream of pulpstock from said tank may be caused to flow upwardly and to spreadlaterally and flow downwardly in a reverse direction, a. foraminoushollow mold having a downwardly directed opening adapted to be placedover the upwardly flowing stream, a vacuum pump, a vacuum jacketdisposed about said mold, a pivotally mounted hollow arm supporting saidjacket and forming a conduit between said jacket and said vacuum pump,means to move said arm about its pivot to move said opening over saidupwardly flowing stream, and means for adjusting the flow of said stockin and the discharge out of said opening while fibres are beingdeposited from said stream upon the interior surface of the walls ofsaid mold.

6. In a process of molding hollow containers w from pulp stock the stepswhich include feeding a stream of pulp stock of restricted cross-sectionupwardly into a hollow foraminous mold, causing said stream to break andspread laterally and downwardly in a direction reverse of said upwardlyflowing stream and over the entire interior surface of said mold whilemaintaining a partial vacuum on the outside of the porous walls of saidmold whereby to deposit pulp fibres from said laterally and downwardlyflowing stream upon said interior surface of the mold and to draw liquidfrom said stream through the pores of said walls, and maintaining theflow of pulp stock in and out of said mold while depositing pulp fibreson said walls from said stock, whereby to selectively deposit the pulpfibres on said mold walls.

'7 In a process of molding hollow containers from pulp stock the stepswhich include projecting a stream of pulp stock upwardly into a hollowforaminous mold through the mouth thereof while maintaining a vacuum onthe outside of the porous walls of said mold, causing said stream tobreak and flow laterally and flow downwardly along the interior surfaceof said mold in a continuous sheet whereby to cause pulp fibres fromsaid stock to be deposited from said flowing sheet of pulp stock on theinterior surface of said mold and to draw liquid from said stock throughthe pores of said walls, maintaining a stream of pulp stock flowing intothe interior of said hollow mold and causing a predetermined amount ofsaid stock entering said mold to flow over the deposited fibres and outof said mold through said mouth while pulp fibres are being deposited onsaid walls from said stock and meanwhile controlling the velocity headof the flowing pulp 'stock whereby to deposit a layer of fibres ofdesired thickness.

8. In a process of forming hollow articles from pulp stock the stepswhich comprise maintaining a supply of said stock containing apredetermined quantity of pulp fibres in water, causing a column of pulpstock drawn from said supply to flow upwardly in a column ofrestricted-crosssection, causing said column to flow through an openinginto a hollow foraminous mold and to flow laterally and downwardly alongthe interior surface of said mold, maintaining a partial vacuum on theexterior of said mold whereby to deposit fibres from said flowing stockon the interior surface of said mold and causing a part of the flowingstock to pass out of said mold in a controlled stream through saidopening while simultaneously depositing fibres on said surface from saidflowing stock.

9. In a process of forming hollow articles from pulp stock the stepswhich comprises maintaining a supply of said stock containing apredetermined quantity of pulp fibres in, water, maintaining afountain-like column of pulp stock drawn from said supply, causing saidfountainlike column to fiow through an opening into a foraminous moldand to spread umbrellawise laterally and downwardly over the interiorsurface of the mold, maintaining a differential pressure between theexterior and interior of said mold whereby to deposit fibres from saidmoving stock on the interior surface of said mold and causing a part ofthe stock of said laterally and downwardly moving stock to pass out ofsaid mold in a controlled stream through said opening whilesimultaneously depositing fibres on said surface from said laterally anddownwardly moving stock.

10. In a process of forming hollow articles from pulp stock, the stepswhich comprise maintaining a supply of said stock containing apredetermined quantity of pulp fibres in water, maintaining 21. geyserof pulp stock drawn from said supply, causing said geyser to flowthrough an opening into a hollow foraminous mold and then laterally anddownwardly in a stream over the interior Walls oi. said mold,maintaining a vacuum on the exterior of said mold whereby to depositfibres from said laterally and downwardly moving stream on the interiorsurface of said mold, causing a part of the stock introduced into themold to pass out of said mold through said opening while simultaneouslydepositing fibres on said surface from said moving stream, and adjustingthe velocity head of said stock by controlling the rate of flow of saidstock both in and out of said mold.

11. In a process of forming hollow articles from pulp stock the stepswhich comprise maintaining a supply of said stock containing apredetermined quantity of pulp fibres in water, maintaining a geyser ofpulp stock drawn from said supply, causing said geyser to flow upwardlythrough an opening into a hollow foraminous mold and then laterally anddownwardly, maintaining a vacuum on the exterior of said mold whereby todeposit fibres from said flowing stock on the interior surface of saidmold, causing a part of the stock of said geyser to pass downwardly outof said mold through said opening while simultaneously depositing fibreson said surface from said geyser and controlling the amount of pulpfibres deposited upon the interior surface of said mold by adjusting thesaid vacuum and the velocity head of said moving pulp stock.

12. A process of forming hollow articles of pulp which co'inprisesmaintaining a supply of pulp stock of predetermined concentration,introducing a restricted stream of pulp stock from said supply upwardlyinto a hollow foraminous mold, causing said upwardly flowing restrictedstream to break and flow laterally and downwardly umbrellawise,maintaining a predeter mined sub-atmospheric pressure on the outside ofsaid mold whereby to deposit pulp fibres from said laterally anddownwardly flowing stream onto the interior surface of said mold,causing a part of said downwardly flowing stream to flow out of saidmold and controlling the velocity of the stream moving through said moldto cause a selective deposition of pulp fibres on the interior of thehollow article being formed whereby to produce a smooth interior surfaceon said article.

13. Apparatus for molding pulp including a hollow foraminous mold havinga downwardly directed restricted opening, means for flowing a column ofpulp upwardly through said mold, and means for controlling the flow ofpulp out of said mold including a battle engirdling said column adjacentthe restricted opening of said mold.

14. Apparatus for molding pulp including a and means mounting saidbaffle and mold for relative adjustment to control the rate of flow ofpulp stock over the interior surface of the mold.

15. Apparatus for molding hollow articles from pulp stock whichcomprises, a supply tank for said stock, an upwardly disposed stationaryjet, a conduit connecting said jet and tank, a centrifugal pumpintermediate said jet and tank to force a column of pulp stock upwardlythrough said jet, means including a by-pass to return a predeterminedpart'of said stock discharged from said pump to said tank and to adjustthe height at which thecolumn of pulp stock discharged through said jetbreaks and flows laterally and downwardly umbrellawise, a hollowforaminous mold having. a downwardly directed charging opening supportedon a pivotally mounted arm and means adapted to adjust said jet relativeto said mold whereby to cause a deposition of pulp fibres of uniformthickness from said laterally and downwardly flowing stock when asuction is applied to the exterior of said mold.

HARVEY V. MITCHELL.

